1. Field of the Invention
This invention relates to analog and digital circuitry and methods, and more particularly to noise-invariant circuits, systems, and methods.
2. Description of the Related Art
U.S. Pat. No. 5,787,029 granted on Jul. 28, 1998 to Edwin de Angel, discloses an ultra low power digital multiplier which uses a modified Booth algorithm to dissipate power proportional to the magnitude of a particular operand, with logic races being eliminated by use of iterative networks. Multipliers are employed in digital filters, digital signal processors (DSP's), and floating point processors, as well as in other complex electrical and electronic systems. One application for such multipliers is in seismic DSP's fir gathering seismic information at selected sensor locations. Such multipliers have a plurality of multiplier rows and activation of particular rows is selectively suppressed to conserve power. Each multiplier row comprises a plurality of blocks of computational logic circuitry. Each block provides a data valid signal to an adjacent block, to enable further processing. The Booth multiplier operates by generating successive partial products from first and second multiplicands comprising overlapping bit groups including a sign bit. According to one construction, a multiplier includes a top row having a plurality of encoders/multiplexers B. A next row includes a plurality of multiplier cells. The multiplier further includes a carry propagate adder having multiplexers, ECDL full adders, and ECDL half adders. The adders and multiplexers have sum and carry outputs, S and C. A NOOP is defined as a triplet 000 or 111, resulting in a zero value addition and not requiring a multiplier row to be turned on. To save power, particular NOOP rows are not turned on, because their being turned on would result in addition of a zero value to the next row while their not being turned on would have the same result. In one multiplier arrangement, a multiplier bus is connected to decoders/multiplexers and multicell circuits. The bus is divided into triplets which are encoded by plural encoders associated with respective multiplier rows. A NOOP signal is passed on particular busses to first row decoders/multiplexers and other row multicell circuits, to indicate particular row skippage. F1 and F2 outputs are provided as to least significant bit content from the decoders/multiplexers to selected least significant multicell circuits. Each row except the first row is provided with switches for receipt of done or start switches, and each row is configured to provide an enable signal to a next in order row at the enable input of one of the two multicell circuits on one end or the other of each row. Upon receipt of an enable signal, each of the multicells activates its adder and then generates a done signal at a done output which in turn activates a next adder, or then signals to the switch in the next row that the present row is finished, or passes an enable signal through an AND gate which is passed to a carry propagate adder. Each of the switches is controlled by a NOOP signal on its associated bus. If the encoded triplet of the received signal is other than a NOOP signal, i.e., a 000 or a 111 code, then the receiving switch signals its receiving row to begin the addition process for that row. If the encoded triplet is 000 or 111, then the enable signal to that row is suppressed by the associated switch and an enable signal is passed to a next in order switch or an AND gate in the case of a last row. When the enable signal is suppressed, the applicable row does not calculate its sums and carrys. Since this data is not available to the next row, each of the multicell circuits also passes the sums and carries from the prior row and makes it available to the next row. Each of the multicell circuits needs to know whether the prior row was a NOOP or a normal operative evolution. This is accomplished with NOOPpast and NOOPpastbar signals.
Unfortunately, the reduced level of power dissipation results in a higher noise level which interferes with quality signal detection and interpretation in connection with sampling operation.
There is a further need for low power operation of in analog and digital subsystems which operate at reduced noise levels in the proximity of sampling operation.